The present invention relates generally to the field of firearms, and more particularly, but not exclusively, to improved cartridge designs.
The most popular cartridge used when firing a firearm is the .22 caliber rimfire cartridge. Rimfire ammunition is often used because it is relatively inexpensive as compared to center fire ammunition. Thus, rimfire ammunition allows greater use of the firearm with less cost for such activities as recreational shooting, weapons training, hunting, and the like. Rimfire ammunition may also be used with firearms that conventionally fire more expensive ammunition, such as military weapons. These types of weapons may be adapted to fire the lower cost rimfire ammunition during training exercises with the firearm, thus saving on training expense.
One example of a rimfire cartridge is illustrated in FIG. 1 and designated generally at 10. Rimfire cartridge 10 includes a bullet 12 connected to a casing 14 at crimped portion 17. Opposite bullet 12, the casing 14 has a rearward end member 16. Casing 14 also includes a wall 22 having an inner surface 22a and an outer surface 22b. Wall 22 and end member 16 define a hollow interior 24. Projecting radially outward from wall 22 and extending between wall 22 and end member 16 is annular outer rim 18. Outer rim 18 defines an annular pocket 20 communicating with hollow interior 24. As is well known in the art, when the cartridge 10 is manufactured, a quantity of fluid priming composition 28 is spun into annular pocket 20 and allowed to dry. A quantity of powder 26 is then placed within hollow interior 24 of casing 14. In order to fire the cartridge, a firing pin configured to sharply strike casing 14 at outer rim 18 crushes the priming composition in annular pocket 20 which in turn ignites powder 26. Powder 26 burns rapidly and creates gas as it burns. The pressure from the gas forces bullet 12 from crimped portions 17 and propels bullet 12 down the barrel of the firearm.
One of the drawbacks with such rimfire cartridges is that casing 14 suffers from low strength and is prone to failure, particularly at rim 18, when casing 14 is used for a high velocity cartridge. Thus, even though the capacity of casing 14 can hold a sufficient quantity of powder to produce a high pressure cartridge, casing 14 will fail due to the higher pressures generated by the larger quantity of burning powder. This results in less powder being used with the cartridge to minimize the risk of casing failure. The reduced amount of powder causes less gas pressure to be generated by the burning powder. This in turn lowers the velocity and the energy of the bullet when it is fired.
Center fire cartridges are popular for their ability to generate high bullet velocities. However, center fire cartridges can be expensive and difficult to manufacture.
There remains a need for cartridges which effectively addresses the problems of casing strength, expense and manufacturing difficulties associated with prior art cartridges. The cartridges should be capable of use in existing firearms with minimum modification to its components, and the cartridges should have application with all caliber firearms. The present invention is directed towards meeting these needs, among others.